Eikon Therapeutics, Inc. reported updated clinical data for its PARP1-selective inhibitor EIK1003 and initial data for its CNS-penetrant PARP1 inhibitor EIK1004 and Werner (WRN) helicase inhibitor EIK1005. The data were presented at the 2026 European Society for Medical Oncology (ESMO) Congress in Madrid, Spain, on October 23, 2026.
The company provided updated results from the Phase 1/2 study of EIK1003, a highly selective non-brain-penetrant PARP1 inhibitor. In Cohort 1A, which treated 65 participants with breast, ovarian, prostate, or pancreatic cancer with homologous recombination repair (HRR) gene mutations, the objective response rate (ORR) was 14.3% (7/49 efficacy-evaluable participants). Responses were observed in ovarian cancer (14.8%), breast cancer (12.5%), and prostate cancer (100%). The median duration of response among confirmed responders was 6.3 months.
In Cohort 1B, EIK1003 was combined with the hormonal agent abiraterone for metastatic prostate cancer. Among 24 efficacy-evaluable participants, the ORR was 20.8% (5/24), with a disease control rate of 83.3%. A PSA response of at least 50% was observed in 30.8% of participants.
In Cohort 1C, EIK1003 was combined with weekly paclitaxel for platinum-resistant ovarian cancer and HER2-negative breast cancer. Among 53 efficacy-evaluable participants, the ORR was 26.4% (14/53), including one confirmed complete response. The company is currently enrolling an additional Cohort 1D evaluating EIK1003 with paclitaxel and platinum-based chemotherapy.
Initial data from EIK1004, a CNS-penetrant PARP1 inhibitor, showed a generally well-tolerated safety profile with minimal hematological suppression. As of the July 13, 2026, safety data cutoff, 68 participants were treated. Grade 3 or higher adverse events occurred in 12 participants (17.6%), with anemia and neutropenia observed in only 1.5% of participants each. The observed ORR was 12.1% (7/58 efficacy-evaluable participants), including one confirmed complete response in breast cancer.
Preliminary data were also presented for EIK1005, a WRN helicase inhibitor. As of the August 20, 2026, safety data cutoff, 10 participants had been dosed with EIK1005 in monotherapy dose escalation, and one participant was dosed in combination with pembrolizumab.
